Timing of Calving Seasons Under the Microscope

Cow-calf pair in a snowy pasture.
Cow-calf pair in a snowy pasture.
(File Photo)

This article was written by Dr. Glenn Selk, Oklahoma State University Emeritus Extension Animal Scientist.

The onslaught of a wet, cold winter has caused some Midwest cattle producers to re-examine the timing of future calving seasons. There will be popular press and social media articles suggesting that calving seasons need to be moved to late spring and early summer. For those regions of the country prone to late winter, spring snowstorms and blizzards, moving the calving season out of these stressful weather events makes sense.

If the calving season is moved to May and June, then the breeding season must be moved to August and September. In the upper Midwest, breeding seasons in the hotter months of summer may be feasible. Although, 90 to 100 degree days may occur, nighttime temperatures will often cool to 70 degrees or lower. However in Oklahoma and Texas, in August daytime temperatures often reach near or above triple digits and night time lows may only cool about 80 degrees. A high pressure heat dome may lock in very hot days and warm nights for an extended period of time. The number of hours each day that the temperature is above the thermal neutral maximum (80 degrees in the bovine) is sizeable. There is little if any opportunity for the cow to dissipate heat in this scenario. Therefore heat stress becomes a biological nemesis to good reproductive performance in late summer months in Oklahoma.

Research conducted several years ago at Oklahoma State University (Biggers, et al, 1986 OSU Animal Science Research Report) illustrated the possible impact of heat stress of beef cows on their reproductive capability. They found that heat stress of beef cows from day 8 through 16 after breeding affected the weights of the conceptus (embryo, fluids, and membranes) and the increased body temperature may have formed an unfavorable environment for embryo survival. The percentage of pregnancies maintained throughout the week of severe heat stress was considerably reduced (83% for non-heat stressed versus 50% for severely heat stressed).

Also research (Meyerhoffer, et al 1985. J. Animal Science 60:352) has clearly shown that semen quality of heat stressed bulls will be significantly reduced and will take nearly 8 weeks after the heat stress to fully recover. When reduced fertility in male is multiplied by reduced embryo survival in the female, percentage calf crops must decline.

Heat stress causes a percentage decrease in pregnancy percentages. It is not an “all or nothing” situation. Spring breeding seasons starting in May and finishing in late June should avoid most of the heat stress in Oklahoma.  This results in February and March calving seasons.  Fall calving (with breeding seasons beginning in late November and ending in January) allow for fertilization and early embryonic survival when heat stress is not a factor. These calves arrive starting in early September.

The best choice for calving seasons will be different for the different climates and weather patterns in the United States.

Background and Research Supporting Caffeine for High-Risk Calves

 
 

Tags

 

Latest News

APHIS Now Thinks Wild Birds Are to Blame for Highly Pathogenic Avian Influenza's Arrival on Four U.S. Dairies
APHIS Now Thinks Wild Birds Are to Blame for Highly Pathogenic Avian Influenza's Arrival on Four U.S. Dairies

The livestock industry continues to grapple with the first confirmed cases of HPAI in cattle, while federal and state agencies continue to assure consumers there's no concern about the safety of the U.S. milk supply.

AABP Creates 'Using Credentialed Veterinary Technicians  in Bovine Practice' Guidelines
AABP Creates 'Using Credentialed Veterinary Technicians in Bovine Practice' Guidelines

Utilizing credentialed veterinary technicians (CVTs) in bovine practice can assist veterinarians in providing additional and efficient services to their large animal clients.

Get the Facts Straight on Highly Pathogenic Avian Influenza
Get the Facts Straight on Highly Pathogenic Avian Influenza

Now that the mystery illness impacting some dairy herds has been revealed as the same strain of Highly Pathogenic Avian Influenza that has been impacting the U.S. poultry flock, pork producers are asking questions.

New Guide Helps Producers Maximize Values of Cull Cows
New Guide Helps Producers Maximize Values of Cull Cows

A new resource developed by the National Cattlemen’s Beef Association and CattleFax helps cattle producers maximize profitability from their culling decisions.

"Boring" Technology Will Reshape Dairy Over the Next 10 Years
"Boring" Technology Will Reshape Dairy Over the Next 10 Years

Once a technology becomes a boring experience it means it has become proven, well-adopted, and easy to utilize. There are three "boring" technologies silently shaping the industry.

Meat Institute: Properly Prepared Beef is Safe to Eat; HPAI is not a Food Safety Threat
Meat Institute: Properly Prepared Beef is Safe to Eat; HPAI is not a Food Safety Threat

According to the Centers for Disease Control and Prevention (CDC) and USDA food safety experts, properly prepared beef is safe to eat and is not a food safety risk to humans.